Zinc is among the most in-demand metals in the world which also means that a considerable amount of this element is released to the environment each year as a result of human activities. A pot experiment was conducted to study the impact of low- and high-dose zinc amendments on plant growth and biomass yield, with Calcic Chernozem as a growing medium and barley (Hordeum vulgare L.) as a model plant. The distribution of zinc in various plant parts was also investigated. Zn (II) was added in powder as bulk ZnO and in solution as ZnO nanoparticles and ZnSO4 in two dosages (3 and 30 mmol kg−1 soil) prior to planting. The plants were harvested after 10 days of growth. The three sets of data were taken under identical experimental conditions. The application of zinc in aqueous solution and in particulate form (having particle sizes in the range of <100 nm to >500 nm) at concentration of 3 and 30 mmol Zn kg−1 to the soil resulted in decreased growth (root length, shoot length) and biomass yield; the only exception was the addition of 30 mmol Zn kg−1 in the form of bulk ZnO, which had a positive effect on the root growth. The dry weight reduction (sprout biomass) was lowest in plants grown in soil treated with dissolved zinc. There were no statistically significant changes in the content of chlorophyll a, chlorophyll b, and total chlorophyll, although flame atomic absorption spectrometry (FAAS) analysis indicated that plants bioaccumulated the zinc applied. This implies that the transport of zinc into the above-ground plant parts is controlled by the presence of effective mechanical and physiological barriers in roots. Crop performance under zinc stress in relation to biomass production and the growth of roots and shoots is also partly a reflection of the effects of soil properties. Our findings emphasize the importance of considering plant-soil interactions in research of potential toxicity and bioavailability of zinc in the environment.
Selenium is a trace element essential for the proper functioning of human body. Since it can only be obtained through our diet, knowing its concentrations in different food products is of particular importance. The measurement of selenium content in complex food matrices has traditionally been a challenge due to the very low concentrations involved. Some of the difficulties may arise from the abundance of various compounds, which are additionally present in examined material at different concentration levels. The solution to this problem is the efficient separation/preconcentration of selenium from the analyzed matrix, followed by its reliable quantification. This review offers an insight into cloud point extraction, a separation technique that is often used in conjunction with spectrometric analysis. The method allows for collecting information on selenium levels in waters of different complexity (drinking water, river and lake waters), beverages (wine, juices), and a broad range of food (cereals, legumes, fresh fruits and vegetables, tea, mushrooms, nuts, etc.).
It is indisputable that separation techniques have found their rightful place in current analytical chemistry, considering the growing complexity of analyzed samples and (ultra)trace concentration levels of many studied analytes. Among separation techniques, extraction is one of the most popular ones due to its efficiency, simplicity, low cost and short processing times. Nonetheless, research interests are directed toward the enhancement of performance of these procedures in terms of selectivity. Dispersive solid phase extraction (DSPE) represents a novel alternative to conventional solid phase extraction (SPE) which not only delivers environment-friendly extraction with less solvent consumption, but also significantly improves analytical figures of merit. A miniaturized modification of DSPE, known as dispersive micro-solid phase extraction (DMSPE), is one of the most recent trends and can be applied for the extraction of wide variety of analytes from various liquid matrices. While DSPE procedures generally use sorbents of different origin and sizes, in DMSPE predominantly nanostructured materials are required. The aim of this paper is to provide an overview of recently published original papers on DMSPE procedures in which metallic nanoparticles and hybrid materials containing metallic particles along with other (often carbon-based) constituent(s) at the nanometer level have been utilized for separation and pre-concentration of (ultra)trace elements in liquid samples. The studies included in this review emphasize the great analytical potential of procedures producing reliable results in the analysis of complex liquid matrices, where the detection of target analyte is often complicated by the presence of interfering substances.
The nanoparticles of TiO2 (TiO2 NP) have been used as a plant-growth stimulant or catalyst in pesticide formulas. However, due to high resistance of TiO2 NP to abiotic weathering, dissolved Ti is unlikely to act as an active compound in these preparations. Even if soil is acidic, TiO2 NP do not dissolve easily and preferably remain as undissolved particles. The low dissolution rates of inorganic nanoparticles in the soil environment make Ti in TiO2 NP largely unavailable for plants and soil microorganisms. To characterize the behavior of TiO2 NP in soil under different pH conditions, we analyzed TiO2 NP-size distribution in two soil materials, an alkaline and acidic one. We also cultivated Aspergillus niger, a fungus ubiquitously found in soils, in the growth medium spiked with TiO2 NP to assess accumulation of the nanoparticles in fungus. In soil suspensions, the dissolved Ti was present in low concentrations (up to 0.010 mg L−1). Most of the TiO2 NP remained in particulate form or appeared as aggregates sized 100–450 nm. In experiment on Ti accumulation by A. niger, TiO2 NP either settled down to the bottom of the flask with growth medium or were actually accumulated by the fungus; about 7.5% of TiO2 NP were accumulated in fungal mycelia. Most of the TiO2 NP remain in particulate form in soil solutions, regardless of soil pH. Filamentous fungus A. niger has the ability to accumulate bioavailable TiO2 NP, which hints at the possibility that some soil fungi can affect spatial distribution of this type of nanoparticles in soils.
The quantification of gold nanoparticles (AuNP) in environmental samples at ultratrace concentrations can be accurately performed by sophisticated and pricey analytical methods. This paper aims to challenge the analytical potential and advantages of cheaper and equally reliable alternatives that couple the well-established extraction procedures with common spectrometric methods. We discuss several combinations of techniques that are suitable for separation/preconcentration and quantification of AuNP in complex and challenging aqueous matrices, such as tap, river, lake, brook, mineral, and sea waters, as well as wastewaters. Cloud point extraction (CPE) has been successfully combined with electrothermal atomic absorption spectrometry (ETAAS), inductively coupled plasma mass spectrometry (ICP-MS), chemiluminescence (CL), and total reflection X-ray fluorescence spectrometry (TXRF). The major advantage of this approach is the ability to quantify AuNP of different sizes and coatings in a sample with a volume in the order of milliliters. Small volumes of sample (5 mL), dispersive solvent (50 µL), and extraction agent (70 µL) were reported also for surfactant-assisted dispersive liquid–liquid microextraction (SA-DLLME) coupled with electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS). The limits of detection (LOD) achieved using different combinations of methods as well as enrichment factors (EF) varied greatly, being 0.004–200 ng L−1 and 8–250, respectively.
Gold nanoparticles (AuNP) are being utilized in an ever-expanding number of applications ranging from scientific research to industrial processes. Increasing nanoparticle emissions in the environment have become of public and academic concern. Since the effects of AuNP on human health are not fully understood, the accumulation of reliable and detailed data is critical for the assessment of their potential risk of harm to humanity. Even their concentrations in natural and engineered water systems do not belong to commonly published data. To obtain such information, the environmental chemists use various sophisticated analytical methods that are often very expensive. Therefore, this paper aims to challenge the analytical potential and advantages of cheaper and equally reliable alternatives that couple the well-established extraction procedures with common spectrometric methods to quantify the ultratrace concentrations of AuNP in complex aqueous matrices. Both types of extraction procedures, solvent extractions as well as sorbent extractions, are discussed in the text. A detailed inspection of different types of interactions that are responsible for the ability to selectively separate AuNP from mixtures containing various ionic species, gold ions, other metallic nanoparticles, and dissolved organic matter can be found in this overview. The examples of the tolerance limits reported for several coexisting components of interest are also given. Practical applications of the extraction procedures, summarized in this article, were demonstrated in analysis of actual environmental matrices, such as tap, river, lake, brook, mineral, and sea waters.
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